.diff

From 5db9543bdf466a7894e5532c10618e42c162da83 Mon Sep 17 00:00:00 2001
From: Josh Allmann <joshua.allmann@gmail.com>
Date: Fri, 24 May 2019 15:30:32 +0000
Subject: [PATCH] lavfi/vf_scale_cuda: Reset frame size after acquiring from
 hwframe.

The first frame is scaled correctly, and subsequent frames are
over-scaled / cropped since the frame data is reset with the
hwframe after each invocation of the scaler.

The hwframe-allocated frame has a width/height that is 32-bit
aligned. The scaler uses this aligned width / height as its target,
leading to "over-scaling" and then cropping of the result.

To generate a broken test sample:

  ffmpeg -hwaccel cuvid -c:v h264_cuvid -i <input> -an \
    -lavfi scale_cuda=w=426:h=240 -c:v h264_nvenc <output>
---
 libavfilter/vf_scale_cuda.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libavfilter/vf_scale_cuda.c b/libavfilter/vf_scale_cuda.c
index 6b1ef2bb6f..13eb3ad24c 100644
--- a/libavfilter/vf_scale_cuda.c
+++ b/libavfilter/vf_scale_cuda.c
@@ -489,6 +489,8 @@ static int cudascale_scale(AVFilterContext *ctx, AVFrame *out, AVFrame *in)
 
     av_frame_move_ref(out, s->frame);
     av_frame_move_ref(s->frame, s->tmp_frame);
+    s->frame->width = s->planes_out[0].width;
+    s->frame->height= s->planes_out[0].height;
 
     ret = av_frame_copy_props(out, in);
     if (ret < 0)
-- 
2.17.1